Throttle-free transmissionless hybrid vehicle

ABSTRACT

In a high speed mode of operating and electric-gas hybrid car, the combustion engine is directly engaged to the wheels without a transmission and that vehicle speed is controlled without a throttle by electric generator loading of the engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/498,804 filed Jul. 7, 2009 now U.S. Pat. No. 7,836,986 entitledTHROTTLE-FREE TRANSMISSIONLESS HYBRID VEHICLE by Marsaili Gillecriosd.

BACKGROUND

Hybrid vehicles of the type having both a combustion engine and abattery-powered electric motor provide greater fuel efficiency or gasmileage than conventional vehicles. Typically, the hybrid vehicle is acompact or light-weight passenger sedan, with the capability ofre-charging the on-board battery from the rotation of the axle or wheel.In some models, the vehicle may also be charged from an electricaloutlet, in the owner's garage for example. The performance of such ahybrid vehicle depends very highly on the vehicle weight. For optimumvehicle performance, the weight is minimized. However, certaincomponents are required that are either costly or heavy, including theengine, transmission, electric motor/generator components, enginethrottle/fuel injection controls. These components also greatly affectthe weight and the cost of the hybrid vehicle.

Among various costly items, a hybrid vehicle requires a complex controlsystem for managing the combustion engine throttle, the power deliveredto the electric motors and the charging of the battery. The controlsystem must coordinate the engine throttle, the electric motor drivepower and the battery-charging current simultaneously in response tochanging acceleration and deceleration commands from the driver. Theneed for the costly or heavy components, including the combustionengine, automatic transmission, electric motor(s), and a complexcontroller limits the degree to which the vehicle efficiency can beimproved or its cost reduced. The controller governs the throttling ofthe engine, and simultaneously manages the power demand on the electricmotors whenever needed to supplement torque if the engine capability isexceeded by the demands to the driver. The controller typicallythrottles the engine so as to optimize its efficiency, by maintainingits torque output above a predetermined fraction of maximum torque, forexample. At the same time, the controller must determine the amount ofsupplementary power from the electric motors required to meet powerdemands. Such a controller is complex and is relatively costly.

SUMMARY

A hybrid vehicle comprises first and second sets of vehicle wheels,first and second motor-generators, a combustion engine and an electricalenergy storage device for powering said motor-generators; a first splinecoupler between said first motor generator and said engine and a secondspline coupler between said first motor-generator and said first set ofvehicle wheels, and a connection between said second motor-generator andone of said first and second sets of wheels. A first shaft speed encodersenses a shaft speed of one of said sets of wheels, a driver interfaceencoder senses a desired vehicle speed, and a comparator senses adifference between said wheel shaft speed and said vehicle speed. Thehybrid vehicle further comprises a feedback loop controller forgoverning an amount of current generated by one of said first and secondmotor-generators in response to said difference so as to reduce thedifference and match the vehicle speed to the desired speed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the exemplary embodiments of the presentinvention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings. It is to be appreciated that certain well knownprocesses are not discussed herein in order to not obscure theinvention.

FIG. 1 is a schematic block diagram of a hybrid vehicle including apower control system in accordance with a first embodiment.

FIG. 2 is a schematic block diagram of a hybrid vehicle including apower control system in accordance with a second embodiment.

FIG. 3 is a schematic block diagram of a hybrid vehicle including apower control system in accordance with a third embodiment.

FIG. 4 is a schematic block diagram of a hybrid vehicle including apower control system in accordance with a fourth embodiment.

FIG. 5 depicts an implementation of an interlocking non-slip coupling orspline coupler employed in the embodiments of FIGS. 1-4.

FIG. 6 depicts a table depicting the state of each system component inthe different operating modes of the power control system of any one ofFIGS. 1-4.

FIG. 7 is a block flow diagram illustrating the operation of acontroller that determines the operating mode of the system of any oneof FIGS. 1-4.

FIG. 8A is a block flow diagram depicting the operation of a “high speedlow battery” mode in accordance with one mode.

FIG. 8B is a block flow diagram depicting the operation of a “high speedlow battery” mode in accordance with another mode.

FIG. 8C is a block flow diagram depicting operation in accordance with afurther mode.

FIG. 9 is a block flow diagram depicting the manner in which the engineis started and then smoothly coupled to the wheels without interruptingvehicle motion.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation. It is to be noted, however, that the appendeddrawings illustrate only exemplary embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

DETAILED DESCRIPTION

A hybrid vehicle is lightened and simplified by eliminating the need forany variable gear transmission and eliminating engine throttle orthrottling. Elimination of the throttle enables the engine to operate ina highly efficient mode. I have discovered that in a high speed mode ofoperating, the combustion engine may be directly engaged to the wheelswithout a transmission and that vehicle speed may be controlled withouta throttle by generator loading of the engine. Generator loading of theengine employs one of two electric motor-generators as a generatordriven by the engine, with the torque loading of the engine by thegenerator being changed to change the vehicle speed in accordance with adesired speed. Generator loading of the engine is also employed afterengine re-start to change the speed of the engine shaft to match thedrive shaft speed prior to engagement of the engine and wheel shafts.

FIG. 1 depicts an embodiment in which the hybrid vehicle powercomponents, including two electric motor-generators, a combustion engineand two spline couplers, are disposed along a common drive shaft axis.The shaft 10-1 of a first electric motor-generator 12 is coupled to theshaft 10-2 of a combustion engine 14 through a motor-engine splinecoupler 16. The shaft 10-1 of the electric motor-generator 12 is alsocoupled through a motor-wheel spline coupler 18 to the shaft 10-3 of asecond electric motor generator 20. The shaft 10-3 of the secondelectric motor generator 20 is connected to a final drive shaft 10-4.The final drive shaft 10-4 is coupled through a conventionaldifferential 22 to a pair of drive wheels 24. Each spline coupler 16, 18is a non-slip coupling and may be engaged and then disengaged undercontrol of a master controller 30. The master controller 30 controlseach of the system components, including the motor-generators 12, 20,the spline couplers 16, 18, for example. Each electric motor-generator12, 20 is of a conventional type that can be controlled to generateelectric current in one mode (generator mode), or to consume electriccurrent to drive the shaft 10 in another mode (motor mode), or to doneither in another mode (neutral mode). In the generator mode, themotor-generator 12 converts the mechanical power or torque delivered bythe engine 14 into an electric current that charges a rechargeableelectrical energy storage device 49. The energy storage device 49 may beimplemented as electric batteries, or a fuel cell or a capacitor, orsimilar devices, or a combination of some or all of the foregoing.Hereinafter, the energy storage device 49 will be referred to“batteries”, with the understanding that the term as used herein refersgenerically any suitable form of a rechargeable electrical energystorage device such as a battery or fuel cell or capacitor orcombination thereof. The motor-generator 20 converts power from thedifferential 22 into a charging current for the batteries 49 in agenerator mode. In a motor mode, the motor-generator 20 convertselectrical power from the batteries 49 into mechanical power to drivethe output shaft 10-4. The master controller 30 controls themotor-generator controller 56, it controls engagement and disengagementof each individual spline coupler 16, 18, and it controls the state ofeach individual motor-generator 12, 20. Specifically, the mastercontroller 30 can switch each motor-generator 12, 20 to any one of threestates: (1) a “motor” state, in which the individual motor-generatoroperates as an electric motor, by converting electricity from thebatteries to mechanical power; (2) a “generator” state, in which theindividual motor-generator operates as an electric generator to convertrotation of its shaft into a battery-charging current; and (3) a neutralmode in which no electrical current flows through the motor-generatorwindings. The charge level of the batteries 49 is provided to the mastercontroller 30 by a sensor 47.

In high speed travel during which the batteries are charged, the vehicleis propelled by the combustion engine 14. Vehicle speed is controlled bythe position of an accelerator pedal 50, which is translated to adesired speed by a signal conditioner 51. Sensors 52 at the drive shaft10-4 constantly sense the actual speed of the vehicle. A comparator 54senses the difference between the actual speed from the sensors 52 andthe desired speed from the signal conditioner 51. This difference isapplied as a control correction signal to a motor-generator controller56. FIG. 1 depicts the motor-generator controller 56 as separate fromthe master controller 30. In an alternative embodiment, themotor-generator controller 56 may be implemented as a part of the mastercontroller 30. The motor-generator controller 56 responds to the controlcorrection signal from the comparator 54 by either increasing ordecreasing the amount of charging current produced by themotor-generator 12, depending upon whether the actual speed exceeds oris less than the desired speed. The comparator 54 determines whether theactual speed exceeds or is less than the desired speed and indicatesthis by the sign of the difference. For this purpose, the comparator 54may provide two difference outputs, namely a magnitude output 57-1 and asign bit 57-2. The controller 56 decrements or increments the chargingcurrent depending upon the sign bit, which is either 1 (positive) or 0(negative). The change in charging current changes the torque loadimposed on the engine 14 by the motor-generator 12. The change in torqueload causes the engine speed (and the wheel speed measured by thesensors 52) to either increase or decrease (in inverse proportion to thechange in torque load) in order to reduce the difference sensed by thecomparator 54. The charging current is changed until the differencesensed by the comparator 54 is nearly zero, at which point the measuredvehicle speed matches (or nearly matches) the desired speed indicated bythe position of the accelerator pedal 50. The comparator 54, the sensors52 and the motor-generator controller 56 constitute a feedback controlloop. This feedback control loop may have a sampling rate at which thecomparator 54 periodically samples the sensors 52, and the controlcorrection signal is updated at the sampling rate. The sampling rate maybe in the range of 10 to 100 Hertz, for example. In a preferredembodiment, the motor-generator 12 has a greater maximum torquecapability than the combustion engine 14. As the amount of chargingcurrent generated by the electric motor-generator 12 is increased, theelectric motor-generator 12 diverts more output torque from the engine14, so that less torque is available to rotate the wheels 24, and thevehicle speed is reduced. In order to increase vehicle speed, thecharging current is reduced, so that less torque is diverted by theelectric motor-generator 12.

No throttling of the engine 14 is performed to change vehicle speed. Theability to control the charging current produced by the motor-generator12 may be realized by providing a current-controlling element 60 inseries with an electro-magnet or field winding of the motor-generator12. The current-controlling element 60 may be of any suitable typeinvolving electronic circuitry, and in particular may be implemented aseither a pulse width modulator or pulse rate modulator, usingconventional techniques. In the case of a pulse width modulator, thecharging voltage or power from the motor-generator 12 is produced as apulse train, and the controller 56 controls the charging current bychanging the pulse width of the pulses. The current-controlling element60 may be provided as internal circuitry of the motor-generator 12. Ifit is desired for the motor-generator 20 to provide the variable torqueload on the engine 14 while charging the batteries 49 (instead of themotor-generator 12), a current-controlling element 62 is connected inseries with an electro-magnet winding of the motor-generator 20 andcontrolled by the controller 56 so as to govern vehicle speed in themanner described above. The current-controlling element 62, like thecurrent-controlling element 60, may be of any suitable type involvingelectronic circuitry, and in particular may be implemented as either apulse width modulator or pulse rate modulator, using conventionaltechniques. In the case of a pulse width modulator, the charging voltageor power from the motor-generator 20 is produced as a pulse train, andthe controller 56 controls the charging current by changing the pulsewidth of the pulses. The current-controlling element 62 may be providedas internal circuitry of the motor-generator 20.

In general, each current-controlling element 60, 62 may be used tocontrol current generated by the respective motor-generator 12, 20 whileoperating in “generator” mode, and may be used to control current flowfrom the batteries 49 to the respective motor-generator 12, 20 whileoperating in “motor” mode.

FIG. 2 depicts a modification of the embodiment of FIG. 1 in which thesecond motor-generator 20 is connected to the drive shaft 70 of a seconddifferential 72 driving a second pair of wheels 74. The firstdifferential 22 is connected to the first motor generator 12 and to thespines 16, 18, but not to the second motor generator 20. The systemcomponents described above with reference to FIG. 1 are present in theembodiment of FIG. 2 and operate in the same manner.

FIG. 3 depicts a modification of the embodiment of FIG. 1, in which thedifferential 22 is associated with a reduction gear 84, 86, and thereare two shafts 10 a and 80 driving the reduction gear 84, 86. The firstmotor-generator 12 and the two spline couplers 16, 18 are connected theone shaft 10 a, while the second motor generator is connected to theother shaft 80. The system components described above with reference toFIG. 1 are present in the embodiment of FIG. 3 and operate in the samemanner.

FIG. 4 depicts and embodiment having three (or more) motor-generators12, 20 and 21, the motor-generator 21 being coupled to the rear wheels.Increasing the number of motor-generators enhances the ability of theon-board controller to maximize available torque under extremely highload conditions (acceleration or hill climbing) by exploiting a largernumber of motor-generators to propel the vehicle together. In this way,a vehicle of superior performance can be realized without requiring thecombustion engine 14 to be enlarged and without requiring anytransmission.

One tutorial example of a spline coupler, corresponding to the splinecoupler 16 or 18, is depicted in FIG. 5, and consists a keyed shaft 40having a shaped key 42 on one end and a receptacle shaft 44 coaxial withthe keyed shaft 40 and having an opening 46 into which the shaped keyfits tightly whenever the two shafts 40, 44 are moved together.

FIG. 6 tabulates the different operating modes of the system and thestates of the individual system components in each operating mode. Thefirst operating mode listed in FIG. 6 is the “slow speed low battery”operating mode. In this mode, the motor-wheel spline coupler 18 isdisengaged to decouple the engine 14 and first motor generator 12 fromthe drive shaft 10-4, while the motor-engine spline coupler 16 isengaged. The engine 14 is running and the first motor-generator 12 is in“charging” mode to charge the batteries 49. The second motor-generator20 is in “motor” mode and rotates the drive shaft 10-4 using electricitydirectly from the motor-generator 12. The mechanical power delivered bythe second motor-generator 20 is governed by the controller 56 throughthe current-controlling element 62 in accordance with the position ofthe accelerator pedal 50.

A second operating mode listed in FIG. 6 is the “slow speed fullbattery” mode. In this mode, the motor-engine spline coupler 16 and themotor-wheel spline coupler 18 are disengaged, so that only the secondmotor-generator 20 is connected to the differential 22. The second motorgenerator 20 drives the wheel 24 by discharging the batteries 49. Theengine 14 is off and the first motor-generator 12 is mechanicallyisolated and may be idle or neutral. Optionally, in this operating mode,the first motor-generator 12 may supplement the driving power of thesecond motor-generator 20 whenever a sudden burst of power is desired.For this purpose, although not indicated in FIG. 6, the motor-wheelspline coupler 16 may be engaged and the first motor-generator 12 mayoperate in its “motor” mode by drawing current from the batteries.

A third operating mode listed in FIG. 6 is one version of a “high speedlow battery” mode. In this version, both spline couplers 16, 18 areengaged, the engine 14 is running and the first motor-generator 12operates in its “generator” mode, while the second motor-generator 20may be in a neutral mode in which the second motor-generator 20 neithergenerates electrical current nor produces mechanical power unless calledupon under a demand for high acceleration or torque. The feedbackcontrol loop (including the sensors 52, comparator 54 and controller 56)is in exclusive control of vehicle speed and governs vehicle speed byvarying the charging current generated by the first motor-generator 12.No throttling of the engine 14 is provided and is not needed to controlthe vehicle speed.

A fourth operating mode listed in FIG. 6 is another version of a “highspeed low battery” mode. In this version, the roles of the twomotor-generators 12, are reversed, so that the first motor-generator isin a neutral mode while the second motor-generator 20 is in itsgenerator mode. The feedback control loop (the sensors 52, thecomparator 54, the controller 56) governs vehicle speed by varying thecharging current generated by the second motor-generator 20 using thecurrent-controlling element 62.

A fifth operating mode listed in FIG. 6 is one version of a “fullbattery low fuel” mode. In this version, the motor-wheel spline coupler18 is engaged to enable the first motor-generator 12 to drive thedifferential 22 by drawing current from the batteries 49. Themotor-engine spline coupler 16 is disengaged to permit the engine to beoff.

A sixth operating mode listed in FIG. 6 is another version of a “fullbattery low fuel” mode. In this version, the roles of the first andsecond motor-generators 12, 20 are reversed, so that the secondmotor-generator 20 propels the vehicle, while the first motor-generator12 is in its neutral mode.

The state of each of the system components (the spline couplers 16, 18,the motor generators 12, 20 and the engine 14) is controlled inaccordance with FIG. 6 by the master controller 30. FIG. 7 is a blockflow diagram depicting how the master controller 30 performs suchcontrol, in accordance with an embodiment. The master controller 30periodically senses the amount of electrical charge stored in thebatteries 49 (block 200 of FIG. 7) and senses the vehicle speed throughthe sensors 52 (block 202 of FIG. 7). The controller 30 then determineswhether the vehicle speed is below a threshold at which the engine 14runs at a predetermined fraction (e.g., 30%) of its maximum torque(block 204 of FIG. 7). If so (“YES” branch of block 204), the controllerdetermines (block 206 of FIG. 7) whether the stored battery charge isbelow a predetermined threshold. If so (“YES” branch of block 206), themaster controller 30 changes the states of the spline couplers 16, 18,the motor-generators 21, 20 and the engine to conform with the “slowspeed low battery” mode of FIG. 6 (block 208 of FIG. 7). Specifically,the controller 30 disengages the motor-wheel spline coupler 18, engagesthe motor-engine spline coupler 16, starts the engine 14, and places thefirst motor-generator 12 into its “generator” mode and the secondmotor-generator 20 into its “motor” mode.

Returning to the determination made in block 206, if it is found thatthe battery charge is not below the predetermined threshold (“NO” branchof block 206), then the master controller 30 changes the states of thespline couplers 16, 18, the motor-generators 12, 20 and the engine 14 toconform with the “slow speed full battery” mode of FIG. 6 (block 210).Specifically, the controller 30 disengages both spline couplers 16, 18,puts the first motor-generator 12 into neutral mode, turns off theengine 14 and puts the second motor-generator 20 into motor mode. Inthis mode, the second motor-generator 20 drives the output shaft 10-4 byconsuming electric current from the batteries 49.

Returning to the determination made in block 204, if the wheel speed isnot below the predetermined velocity threshold (“NO” branch of block204), then a determination is made of whether the battery charge isbelow the predetermined charge threshold (block 212). If so (“YES”branch of block 212), the master controller 30 changes the states of thespline couplers 16, 18, the motor-generators 12, 20 and the engine 14 toconform with the “high speed low battery” mode of FIG. 6. Specifically,the master controller causes both spline couplers 16, 18 to be engaged,starts the engine, and puts at least one of the motor-generators 12 or20 into its “generator” mode so as to draw torque from the engine 14 tocharge the batteries 49 (block 214). This enables the feedback controlloop (the sensors 52, the comparator 54 and the motor-generator currentcontroller 56) to govern vehicle speed by varying the motor-generatorcharging current, in the manner described above.

Returning to the determination made in block 212, if it is found thatthe batteries are not low (“NO” branch of block 212), then the mastercontroller 30 determines whether the fuel supply is low or below apredetermined fuel threshold (block 216). If the fuel is low (“YES”branch of block 216), then the master controller 30 changes the statesof the spline couplers 16, 18, the motor-generators 12, 20 and theengine 14 to conform with the “full battery low fuel” mode of FIG. 6(block 218). Specifically, the controller 30 disengages the splinecoupler 16 and engages the spline coupler 18, puts the firstmotor-generator 12 into neutral mode and puts the second motor-generator20 into motor mode. Otherwise (“NO” branch of block 216), the mastercontroller 30 configures the system for running at high speed with fullbatteries by propelling the vehicle from either one (or both) of the twomotor-generators using battery current (block 220).

FIG. 8A is a block flow diagram depicting the operation of the “highspeed low battery” mode of block 214 of FIG. 7 in accordance with afirst embodiment of this mode. In this mode, the first electric motorgenerator 12 imposes a torque load on the engine 14 (block 300 of FIG.8A). For this purpose, both spline couplers 16, 18 are engaged and themotor-generator 12 operates in its “generator” mode in which it convertsmechanical power from the engine 14 into electrical power for chargingthe batteries 49, as described above. The second motor-generator 20 maybe neutral, except when called upon under a high torque demand. In analternative embodiment, the roles of the two motor-generators 12, 20 arereversed, so that the first motor-generator 12 is neutral while thesecond motor-generator 20 operates in motor mode to provide a torqueload on the engine 14, under control of the feedback control loop 52,54, 56 operating in the manner described above. No throttle is requiredand no throttling of the combustion engine 14 is performed so that theengine 14 is operated in effect without a throttle (block 302). Thecomparator 54 samples the present position of the accelerator pedaloperated by the driver (block 304) and compares the pedal position withthe position sensed during the previous sampling (block 306) todetermine whether the pedal position is more depressed or less depressedsince the previous sample (block 307). If the latest pedal position ismore depressed, the motor-generator controller 56 decrements thecharging current that the motor-generator 12 is allowed to produce(block 308), causing the engine speed to increase. The amount by whichthe current is decremented may be proportional to the magnitude of thedifference sensed by the comparator 54. If the present pedal position isless depressed than the previous one, then the motor-generatorcontroller 56 increments the charging current that the motor-generator12 is allowed to produce (block 310), thereby causing the engine speedto slow. The amount by which the current is incremented may beproportional to the magnitude of the difference sensed by the comparator54. The controller 30 then returns to block 304 to complete a controlcycle consisting of the blocks 304, 306, 308 and 310. This cycle isrepeated at a rate determined by the controller.

FIG. 8B is a block flow diagram depicting the operation of the “highspeed low battery” mode of block 214 of FIG. 7 in accordance with asecond embodiment of this mode. In this mode, the first electric motorgenerator 12 imposes a torque load on the engine 14 (block 300′ of FIG.8). For this purpose, both spline couplers 16, 18 are engaged and themotor-generator 12 operates in its “generator” mode in which it convertsmechanical power from the engine 14 into electrical power for chargingthe batteries 49, as described above. The second motor-generator 20 maybe neutral.

In an alternative embodiment, the roles of the two motor-generators 12,20 are reversed, so that the first motor-generator 12 is neutral whilethe second motor-generator 20 operates in motor mode to provide a torqueload on the engine 14, under control of the feedback control loop 52,54, 56 operating in the manner described above. No throttle is requiredand no throttling of the combustion engine 14 is performed so that theengine 14 is operated in effect without a throttle (block 302′). Thecomparator 54 receives the vehicle velocity desired by the driver (block304′) and receives the instantaneous actual vehicle velocity from thesensors 52 (block 306′) to perform a comparison (block 307′). If thevehicle speed is less than the desired speed, the motor-generatorcontroller 56 decrements the charging current that the motor-generator12 is allowed to produce (block 308′).

The amount by which the current is decremented may be proportional tothe magnitude of the difference sensed by the comparator 54. If thevehicle speed is greater than the desired speed, the motor-generatorcontroller 56 increments the charging current that the motor-generator12 is allowed to produce (block 310′). The amount by which the currentis incremented may be proportional to the magnitude of the differencesensed by the comparator 54. The controller 30 then returns to block304′ to complete a control cycle consisting of the blocks 304′, 306′,308′ and 310′. This cycle is repeated at a rate determined by the rateat which the sensors 52 provide updated measurements of vehicle speed.

In yet another embodiment, the generator loading of the engine 14 isdetermined in direct proportion to the position of the accelerator pedal50. Thus, under deceleration, the motor-generator 12 (and/or themotor-generator 20) is operated so as to impose a greater generator loadon the engine 14 (to slow it down) as the accelerator pedal 50 is lessdepressed (as the driver begins to let up on the accelerator pedal 50).Under acceleration, as the accelerator pedal is depressed more, thegenerator loading of the engine 14 is decreased (to enable it to speedup). As the pedal 50 is further depressed, the battery charging currentis eventually decreased to zero (no generator loading). At this point,the engine 14 is producing its maximum torque and requires assistancefrom the motor-generator 12 for any further increase in speed.Therefore, at this point, the motor-generator 12 is switched from its“generator” mode to its “motor” mode, in which it provides more torquefor the vehicle, the added power being determined by the position of theaccelerator pedal 50, which in turn determines the current drawn by themotor-generator 12 from the batteries 49. As the accelerator pedal 50 isdepressed even further, greater torque is attained by running bothmotor-generators 12 and 20 in the “motor” mode so that they both providetorque. The controller permits the motor-generators 12, 20 to drawincreasingly greater current from the batteries 49 as the acceleratorpedal continues to be further depressed. At maximum pedal depression(“floored”), both motor-generators draw the maximum amount of currentfrom the batteries. Performance can be further enhanced by providingmore on-board motor-generators to draw upon (without increasing enginesize). Performance may also be enhanced by including, in the energystorage device 49, a capacitor or similar device capable of providing agreater current.

Aspects of this latter embodiment are depicted in FIG. 8C. First, theengine 14 and the motor-generator 12 are coupled together by the spline16, while the other motor-generator 20 is neutral/idle (block 320 ofFIG. 8C). The comparator 54 senses (samples) the latest change in theposition of the accelerator pedal 50 (block 325). This sampling isperformed repetitively at a rate determined by the controller 56 or thecontroller 30. If the change in pedal position indicates a demand fortorque within the capability of the engine 14, the motor-generator 12 isoperated in “generator” mode (block 330). In this mode, the controller56 responds to the sensed change in pedal position by changing generatorloading of the engine 14 by the motor-generator 12 (by increasing ordecreasing the charging current to the batteries 49 from themotor-generator 12). Such changes, in one embodiment, may beproportional to the change in pedal position, and may be an increase ordecrease in current, depending upon the direction of the pedal positionchange. Otherwise, if the demand for torque is beyond the capability ofthe engine 14 (block 340), then the motor-generator 12 is operated in“motor” mode, drawing current from the batteries 49. In this mode, thebattery current to the motor-generator 12 is changed in accordance withthe sensed change in pedal position. In one embodiment, this change maybe proportional to the change in pedal position, and may be an increaseor decrease in current, depending upon the direction of the pedalposition change. If the torque demand is even greater, beyond thecapability of the combination of the engine 14 and the motor-generator12 (block 350), the motor-generator 20 (which coupled to the wheels) isactivated, and both of the motor-generators 12 and 20 are operatedsimultaneously in “motor” mode. In this mode, the battery current to themotor-generators 12 and 20 is changed in accordance with sensed changein pedal position. This change may be proportional to the pedalposition, and may be an increase or decrease in current, depending uponthe direction of the pedal position change. The system can revert to anyof the three modes (of blocks 330, 340 and 350), depending upon thecurrent torque demand. The master controller 30 or the controller 56 maydetermine the torque demand simply by noting the change in position ofthe pedal 50.

The sensing step of block 325 is performed repetitively at apredetermined rate. Each time this step is performed, the system mayenter into any one of the modes of blocks 330, 340 and 350, so that asmooth transition between these modes is realized as the driverdepresses and releases the accelerator pedal 50 while the vehicle isoperated in the high speed low battery mode of block 214 of FIG. 7.

As described previously herein, in a high speed mode in which thecombustion engine 14 directly drives the differential 22, the systemregulates vehicle speed without throttling the combustion engine 14 bychanging the load imposed on the engine 14 by the motor-generator 12operating as a generator to charge the batteries 49. This may bereferred to as generator-loading of the engine. Generator-loading of theengine is also employed during engine restart to control engine shaftspeed without requiring any throttling of the engine. Themotor-generator 12 is first employed in “motor” mode as a starter motorto re-start the engine 14 using electrical power from the batteries,while both the engine 14 and the motor-generator 12 are decoupled fromthe differential 22 by disengagement of the motor-wheel spline coupler18. As soon as the engine has re-started, the motor-generator 12 ischanged to “generator” mode to impose a torque load on the engine 14.The master controller 30 causes the motor-generator controller 56 tochange the charging current of the motor-generator 12 so as to adjustthe shaft speed of the engine 14. A shaft speed sensor 100 at the outputshaft 10-1 of the motor-generator 12 (or at the output shaft 10-2 of theengine 14) furnishes the master controller 30 with instantaneousmeasurements of engine shaft speed. The master controller also sensesthe speed of the output drive shaft 10-4 by the sensor 52 referred topreviously herein. As soon as the engine shaft speed matches the speedof the drive shaft 10-4, the master controller 30 causes the motor-wheelspline coupler 18 to engage, so that the engine 14 then powers thevehicle. This engine restarting process is described in detail below.

In FIG. 7, some transitions may be made between an operating mode inwhich the combustion engine 14 is off and another mode in which thecombustion engine 14 is running. FIG. 9 is a block flow diagramdepicting how such a transition is made by the master controller 30.First, while the engine is still off, the spline couplers 16, 18 aredisengaged (block 400 of FIG. 9), and the shaft velocity of the firstmotor-generator 12 is brought to zero (block 405 of FIG. 9). Then, themotor-engine spline coupler 16 is engaged (block 410) and themotor-generator 12 is rotated in motor mode using battery power (block412), while the ignition circuits of the engine 14 are activated,causing the engine 14 to start (block 414). As soon as the engine 14 hasstarted, the state of the motor-generator 12 is changed to conform withthe desired operating mode (block 416). For example, for the “high speedlow battery” operating mode, the state of the first motor-generator 12is changed, after the engine 14 starts, from “motor” mode to “generator”mode. Then, the speed of the engine shaft 10-2 is matched to the speedof the drive shaft 10 a by the controller 56, under control of themaster controller 30, controlling the current controlling element 60 ofthe motor-generator 12 so as to control the torque load on the engine 14(block 418). In order to bring the speed of the engine shaft 10-2 closeto the speed of the drive shaft 10-4, the master controller 30 monitorsthe difference between the motor shaft speed and the drive shaft speedand changes the charging current of the motor-generator 12 so as toreduce the difference until the two shaft speeds match. Once the engineshaft speed matches that of the drive shaft 10 a, the motor-wheel splinecoupler 18 is engaged, coupling the engine 14 to the wheels 24 in asmooth manner (block 420).

Referring to FIG. 1, the master controller 30 carries out this speedmatching function by comparing the drive shaft speed (sensed by thesensors 52) with the speed of the motor shaft 10-1 (sensed by the sensor100 on the motor shaft 10-1). The difference sensed by the mastercontroller 30 is transformed to a command signal. The master controller30 applies the command signal to the motor-generator controller 56. Themotor-generator controller 56 changes the amount of charging currentproduced by the motor-generator 12 in accordance with the commandsignal, so as to adjust the torque load imposed on the engine 14 by themotor-generator 12, and bring its shaft speed closer to that of thedrive shaft 10-4. The adjustment is made in accordance with the sign ofthe difference (determining whether the current should be increased ordecreased). The magnitude of the adjustment to the charging current maybe a predetermined increment or may be an amount proportional to themagnitude of the difference. This adjustment is carried out repetitivelyuntil the two shafts rotate at the same speed and the motor-wheel splinecoupler 18 can be engaged. Generator loading of the engine is thenemployed as described above to constantly match the vehicle speed to adesired speed signaled by the accelerator pedal position.

The embodiment of FIG. 4 may be expanded to provide a fourthmotor-generator (not shown). In this case, each of the fourmotor-generators may be adapted to independently drive a different oneof the four wheels of the vehicle, for four-wheel drive.

For heavy load applications involving continuous high torque loads overseveral hours, a second combustion engine (not shown) may be providedwhich may be decoupled and inactive until activated and coupled to thewheels during sustained high torque operation to supplement the torqueprovided by the first combustion engine 14.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A hybrid vehicle comprising: vehicle wheels, first and secondmotor-generators, a combustion engine and an energy storage device; afirst coupler between said first motor generator and said engine and asecond coupler between said first motor-generator and one of saidvehicle wheels, and a coupling between said second motor-generator andsaid one or another one of said vehicle wheels; a driver-operated pedaland a comparator for sensing a position of said pedal; a mastercontroller responsive to said position of said pedal and comprising acommand signal output; a current controller coupled between said energystorage device and one of said electric motor-generators, said currentcontroller comprising a current control signal input; a signal pathbetween said command signal output and said current control signalinput; wherein said first and second couplers are engagable anddisengagable under control of said master controller, and wherein saidvehicle is configurable into: (A) a low speed configuration in which:(a) one of said motor generators is coupled to said wheels and isconnected to receive current from at least one of said energy storagedevice or the other of said motor generators, and (b) the other one ofsaid motor generators is coupled to be driven by said engine and isconnected provide current to said energy storage device or to the onemotor generator; and (B) a high speed configuration in which: (a) saidengine is coupled to said wheels, (b) a selected one of said motorgenerators is coupled to said engine, and (c) said selected one motorgenerator is connected through said current controller to providecurrent to said energy storage device.
 2. The hybrid vehicle of claim 1further comprising a vehicle speed sensor comprising a speed signaloutput coupled to said vehicle controller.
 3. The hybrid vehicle ofclaim 2 wherein said controller is programmed to configure said vehicleinto said low speed configuration upon said speed output signalcorresponding to a vehicle speed below a predetermined threshold and toconfigure said vehicle into said high speed configuration upon saidspeed output signal corresponding to a vehicle speed above apredetermined threshold.
 4. The hybrid vehicle of claim 1 wherein eachone of said first and second couplers comprises a disengagable splinecoupler.
 5. The hybrid vehicle of claim 1 wherein said coupling isbetween said second motor generator and said one of said vehicle wheels,and wherein said second motor generator is coupled between said one ofsaid vehicle wheels and said second coupler.
 6. The hybrid vehicle ofclaim 1 wherein each of said first and second couplers is disengagableunder control of said master controller.